Rubber compositions stabilized with 6-diethylamino substituted 1, 2-dihydroquinolines



RUBBER COR [POSITIONS STABILIZED WITH 6-DI- ETHYLAMINO SUBSTITUTED 1,2 DIHYDRO- QUINOLINES David J. Beaver, Richmond Heights, M0., Paul M. Downey, Gainesville, Fla, and James 0. Harris St. Albans, W. Va., assignors to Monsanto Chemical Company, St. Louis, Mo, a corporation of Delaware No Drawing Original application August 4, 1953, Serial No. 372,399, now Patent No. 2,713,047, dated July 12, 1955. Dividedand thisapplicah'on January 7, 1955, Serial No. 480,618

6 Claims. (Cl; zoo-45.3)

' on CEHE RI on, R

where R represents hydrogen or an alkyl substituent, as for example methyl, ethyl,'propyl, isopropyl, and butyl radicals. 'R represents a'short chain alkyl radical such as methyl, ethyl,- propyl or butyl.

The new compounds possess valuable properties which render them siutable for a number of uses, outstanding of which is an adjuvant for rubber compounding. 1 One of the major problems of the rubber industry is protection of natural and synthetic rubber goods against exposure cracking, that is degradation due to ozone while the rubber article is under either static or dynamic stress. The problem is a difficult one and is aggravated by the fact that in general chemical antioxidants or age retarders have little or no value in protecting against deterioration by ozone. The new compounds are efiicient anti-exposure cracking agents for sulfur vulcanizable elastomers.

The following examples of the invention illustrate the preparation of the new compounds in detail:

Example 1 Into a suitable reactor fitted with a feed line for passing in acetone and a trap for collecting by-product water of condensation, there was charged 49.2 grams of N,N- diethyl-p-phenylenediamine and 3.5 grams of toluenesulfonic acid. The mixture was heated to 135 C. and acetone passed in at the rate of approximately 2.5 moles per hour per mole of amine charged until 13.6 ml. of water were collected. The volatile constituents from the reactor were fed to the center of a fractionating column where the unreacted acetone was stripped out and fed back to the reactor, the by-product water being collected in a reboiler at the bottom of the column maintained at 100 C. The product was then heated under reduced pressure for about 30 minutes to remove any readily volatile constituents remaining. The crude product weighed 78.6 grams. The product was further purified by fractional distillation. The 6-diethylamino-1,2-dihydro-2,2,4-trimethylquinoline had a boiling point of 115-120 C./1 mm, n =1.5718.

Example 2 Into a reactor fitted with a reflux condenser there was charged 55.4 grams of 6-diethylamino-1,2-dihydro-2,2,4-

represented by F I 1C 2,805,212

j -P atented Sept. 3, 1957 trimethylquinoline, 32.1 grams of methyl iodide, 26.6 grams of.. s odiu1n carbonate and 280 ml. otwaterr The mixture was. heated. at refluxing temperature for about 12 hours, the .organic: layer separated and distilled under .reduced pressure. The 6-diethylamino-1,2-dihydro-1,2,2,4- tetramethylquinolipe was separated from the crude. reaction mixture by distillation at reduced pressure. .As illustrated, the preparation of thenewcompounds is affected by condensing N,N-diethyl-p-phenylenediamine With a methyl ketonein amolar ratio of atleast 1:2,in the presenceof' a suitable catalyst, such as toluenesulfonic acid, benzenesulfonic acid, sulfuricgacidgiodine or bromine. .Examples of suitablemethyl' ketones' are acetone, methyl ethyl betone,'met hyl isopropyl ketone, and methyl butyl ketone. Forintroducing an alkyl substituent in the 1-position of a 6-diethylamino-l,2-dihydro-2,2,4-trialkylquinoline the iodides are the most satisfactory due to their greater reactivity. However, the bromides are adequate in many instances and in some cases chlorides condense satisfactorily. Thereactivity of chlorides is enhanced sharply by using them in conjunction with a small amount of potassium iodide.

Further examples of the invention are:

6 diethylaminp i .1,2 dihydro 2,4 diethyl 2 methylu ql nc 6 diethylamino 1,2 dihydro 1 methyl 2,4 diethyl 2-methy1quino1ine 6 diethylamino 1,2 .-.di hydro 1 ethyl 2,2,4 trimethylquinoline p 7 7 V 6 diethylamino 1,2 dihydro' 1 butyl 2,2,4 trimethylquinoline As illustrative of the anti-exposure cracking properties in vulcanized sulfur vulcanizable synthetic rubber-like materials, stocks were-prepared from butadiene-1,3-styrene copolymer compositions utilizing the following ingredients:

S took A B 40 GR-S parts by weight. 100 100 Carbon black .do 50 Saturated hydrocarbon softener do 10 10 Zinc ox .do 4 4 Stearic acid -do 2 2 5 Sulfur d0 1. 75 1. 75 N -cyc1ohexyl enzothiazole su enamide .do. 17 2 1. 2 6-Dlethylamiuo-1,2-dihydro-2,2,4-trimethylquin0line parts by weight. 1. 5

The stocks so compounded were cured in a press for 30 minutes at 144 C. The vulcanizates were evaluated under dynamic conditions in an atmosphere containing a definite concentration of ozone. Samples of the stocks were cured in the form of a belt /2" wide, A" thick and 5 diameter and mounted on 1" diameter shafts. The ozone concentration was maintained at 20-30 parts per hundred million throughout the test and the shafts were rotated at R. P. M. In this manner a momentary elongation through a range of 0-20% was provided at any portion of the test specimen passing over the shaft. (The apparatus and procedure employed is described in a paper of Creed et a1. entitled An Apparatus for the Evaluation of Ozone Protective Agents for Elastomers Under Dynamic Conditions, given at the Cincinnati, Ohio, meeting of the Rubber Division of the American Chemical Society May 1, 1952.) The experimental test specimens were compared visually at various intervals noting the extent of cracking. A stock which is severely cracked has no service life remaining in terms of the useful life of a rubber article and where the cracking is designated as extremely severe the degradation is well beyond even this point. The results of the tests are set forth below:

where R is selected from the group consisting of hydrogen and alkyl radicals containing one to four carbon atoms and R represents an alkyl radical of one to four carbon atoms. r

; 2. A composition comprising vulcanized diene hydrocarbon rubber and in amount sutficient to inhibit exposure cracking a compound of the general formula 4 where R represents an alkyl radical of one to four carbon atoms.

3. A composition comprising vulcanized diene hydrocarbon rubber and in amount sufficient to inhibit exposure cracking a compound of the general formula CH: CgHg on OaHs /('}GH:

where R represents an alkyl group of less than three carbon atoms.

4. A composition comprising vulcanized diene hydrocarbon rubber and in amount suflicient to inhibit exposure cracking 6-diethy1aminog-1,2-dihydro-2,2,4-trimethylquinoline, said rubber being a butadiene-styrene copolymer. 5. A composition comprising vulcanized diene hydrocarbon rubber and in amount suflicient to inhibit exposure cracking 6-diethylamino-1,2-dihydro-1,2,2,4-tetramethylquinoline, said rubber being a butadiene-styrene copolymer. c

6. A composition comprising vulcanized diene hydrocarbon rubber and in amount sufiicient to inhibit exposure cracking G-diethylamino-l,Z-dihydro-2,4-diethyl-2-methylquinoline, said rubber being a butadiene-styrene copolymer.

References Cited in the file of this patent UNITED STATES PATENTS 2,530,774 Kehe et al Nov. 21, 1950 2,713,047 Beaver et al July 12, 1955 OTHER REFERENCES Davis and Blake: Chemistry and Technology of Rubber,

1937, pages 432 and 435. 

1. A COMPOSITION COMPRISING A SULFUR VULCANIZABLE DIENE HYDROCARBON RUBBE RAND IN AMOUNT SUFFICIENT TO INHIBIT EXPOSURE CRACKIING A COMPOUND OF THE GENERAL FORMULA 